Endochondral growth will be studied in rats, calves and human epiphyses. The relationship of the relatively inextractable proteoglycans, resistant proteoglycans, and the modified proteoglycans derived therefrom, shall be studied by histochemical, electron microscopical and biochemical means in order to elucidate the possible role of these proteoglycans in endochondral growth and cartilage clacification. An aspect of the research is to devise a means for liberating the resistant proteoglycans in such a state that they will be amenable to structural studies. The liberated resistant proteoglycan will be chemically dissected in the hope of determining a possible linkage between proteoglycan and collagen. It is also planned to solublize and determine some of the chemical and structural features of the proteoglycans in calcified cartilage.